The present invention relates to an insulator used for a fuel cell.
JP2008-251309A proposes a fuel cell which secures an insulation resistance by disposing an insulator between a current collector and an end plate which are disposed at one end of a fuel cell stack.
Recently, a reduction in size of components which do not contribute to an output of the fuel cell is demanded in order to improve a power density (output energy per unit mass or unit volume) of the fuel cell. Since the insulator described above does not contribute to the output of the fuel cell, there is a request of reducing the thickness of the insulator while maintaining the thickness sufficient for securing an insulation distance. However, when reducing the thickness of the insulator, a poor insulation resulting from a generation of pinholes and a poor insulation resulting from mixing of conductive materials with the insulator material when manufacturing the insulator may occur. Note that the subject described above is common to a structure in which an insulator is disposed between an arbitrary end member disposed outside of one end of a fuel cell stack not limited to the end plate) and a current collector. The end member includes, for example, a pressure plate which presses the fuel cell stack accommodated in a case toward the current collector, in addition to the end plate.